1. Field of the Invention
The present invention relates to electrodes for a Group III nitride compound semiconductor having p-type conduction, a Group III nitride compound semiconductor device having this type of electrodes, and methods of forming these electrodes. Especially, the invention relates to electrodes for a Group III nitride compound semiconductor having p-type conduction with improved ohmic characteristics, adhesive strength and contact resistance between the semiconductor and the electrodes.
2. Description of Background Information
Conventionally, gold (Au) that is deposited on a surface of a p-type conductive gallium nitride (GaN) layer is used as an electrode. However, because the adhesive strength between the Au and the GaN layer is poor, an electrode layer made of Au peels easily away from the GaN layer during alloying processes performed on the GaN layer.
Nickel (Ni) is interposed between the Au electrode layer and the GaN layer so as to improve the adhesive strength, This arrangement, however, leads to poor ohmic characteristic of the semiconductor and high contact resistance between the GaN layer and the Ni.